The invention relates to an optical device and means for connecting such an optical device to other devices. In particular, the invention relates to achieving good optical connection by effective abutment of optical faces of optical fibres. Many forms of optical connector involve connection of optical fibres such that opposing faces of the optical fibres are urged together into contact. It is known that effective coupling through abutment of faces may involve a measure of buckling of one or both fibres. This is discussed in, for example, U.S. Pat. No. 4,727,742. In this connector two optical fibres are butt spliced in a passage in the connector until a measure of buckling of fibres occurs. At this point the fibres are crimped into position.
An alternative solution is adopted in U.S. Pat. No. 4,907,335. In this patent a connector is described in which one or more of the optical fibres is mounted within the connector so that it is bent, all before the faces of the fibres are brought into contact. This is done to prevent excessive pressure from damaging the optical faces.
These solutions are relatively complex to manufacture, particularly for a low cost connector. For low cost connectors, it is desirable to achieve a coupling solution which is reliable yet which involves a simple assembly step. An example of a system in which a very low cost connection solution is desirable is a non-hermetic optical device, such as a laser transmitter, photodetector receiver, or tranceiver, connectorised with a standard connector such as an MT connector. In an appropriate form of such a device the active optical device is connected to an MT connector body by a short length of fiber. Typically, there will be more than one device, each connected to the MT connector by its own length of fiber (e.g. a tranceiver comprising both a laser transmitter and a photodetector receiver). This fiber within the MT connector of the connectorised device contacts the optical fiber in a further MT connector attached to, for example, a cable to convey optical signals to or from the device. Such a system is appropriate for very low cost applications, and therefore it is particularly desirable in such a system to achieve a cheap yet effective solution to guarantee effective coupling between fibres in MT connectors.
In a first aspect, the invention provides an optical connector, comprising: a housing part having a fiber bore therethrough and having a housing connecting face for abutment or adjacence with a housing connecting face of a mating optical connector; and an optical fiber located in the fiber bore and fixed to the housing part, the optical fiber having a fiber connecting face;wherein the optical fiber protrudes from the housing part at the housing connecting face, such that the fiber connecting face is displaced by a protrusion distance from the housing connecting face, the protrusion distance being between 5 xcexcm and 100 xcexcm. Advantageously, the housing part is an MT connector housing part. In a related aspect of the invention, there is provided a connectorised optical device comprising an optical connector as indicated above and an optical device, wherein the optical device is adapted to send or receive light through the optical fiber of the optical connector.
In a further aspect, the invention provides a connecting means between two optical components, the first optical component comprising a first optical fiber and a first housing part, and the second optical component comprising a second optical fiber and a second housing part, wherein there exists a position of mating contact between the first housing part and the second housing part, and in this position of mating contact a housing connecting face of the first housing part is adapted to be in abutment with a housing connecting face of the second housing part, and there exists a position of fiber contact in which a fiber connecting face of the first optical fiber and a fiber connecting face of the second optical fiber are just in contact with no force urging one fiber connecting face towards the other fiber connecting face; such that there exists a protrusion distance, which is the distance which the first housing part must travel relative to the second housing part to reach the position of mating contact from the position of fiber contact; wherein the protrusion distance lies between 5 xcexcm and 100 xcexcm.
Conventionally, the fiber in an MT or a similar connector protrudes for approximately 1 to 2 xcexcm. This is a relatively short distance, and it is hard to control this distance precisely in manufacture. In practice, it can be found that the fiber in an MT connector is even slightly recessed with respect to the body of the connector. With no other component present to control the contact between fiber faces, it is found that the optical contact achieved by such connections alone does not reliably achieve a high-quality connection. It is found in the present invention that use of a significantly greater protrusion, in the range of 5 to 100 xcexcm, but advantageously 10 to 20 xcexcm, allows satisfactory contact quality to be achieved between the two connector faces without forces arising which are sufficiently great to damage the fibres or otherwise affect the optical connection. The resilience of the fiber itself is used to bring the two faces into positive contact.
The effectiveness of this solution is surprising in the light of the prior art, especially U.S. Pat. No. 4,907,335, which teaches against allowing optical fibres to buckle on coming into contact.